Lubricant composition comprising branched diesters and viscosity index improver

ABSTRACT

The invention refers to lubricant compositions comprising a specific diester together with a viscosity index improver.

TECHNICAL FIELD

This application relates to lubricant compositions comprising brancheddiester compounds in association with a viscosity index improver. Thecompositions can be used to reduce the fuel consumption and to improvethe cleanliness of an engine, especially a car engine.

BACKGROUND

Lubricants are widely used to reduce friction between surfaces of movingparts and thereby reduce wear and prevent damage to such surfaces andparts. Lubricants are composed primarily of a base stock and one or morelubricant additives. The base stock may be a relatively high molecularweight hydrocarbon. In applications where there is a large amount ofpressure applied to moving parts, lubricating compositions composed onlyof hydrocarbon base stock tend to fail and the parts become damaged. Thelubricant manufacturer is in constant need to improve their formulationsto address increased demands on fuel economy while balancing the need toimprove the cleanliness of the engines or to reduce emissions. Thesedemands force manufacturers to address their formulation capabilitiesand/or look for new base stocks that can meet the performancerequirements.

To make lubricants, such as motor oils, transmission fluids, gear oils,industrial lubricating oils, metal working oils, etc., one starts with alubricant grade of petroleum oil from a refinery, or a suitablepolymerized petrochemical fluid. Into this base stock, small amounts ofadditive chemicals are blended therein to improve material propertiesand performance, such as enhancing lubricity, inhibiting wear andcorrosion of metals, and retarding damage to the fluid from heat andoxidation. As such, various additives such as oxidation and corrosioninhibitors, dispersing agents, high pressure additives, anti-foamingagents, metal deactivators and other additives suitable for use inlubricant formulations, can be added in conventional effectivequantities. It has long been known that synthetic esters can be usedboth as a base stock and as an additive in lubricants. By comparisonwith the less expensive, but environmentally less safe mineral oils,synthetic esters were mostly used as base oils in cases where theviscosity/temperature behavior was expected to meet stringent demands.The increasingly important issues of environmental acceptance andbiodegradability are the drivers behind the desire for alternatives tomineral oil as a base stock in lubricating applications.

SUMMARY OF THE INVENTION

The invention provides a lubricant composition comprising at least onecompound of formula (I) below and at least one viscosity index improver

wherein:

n is below 1.1

R1 represents a linear or branched, saturated or unsaturated C3-C20,

R′ represents a linear or branched, saturated or unsaturated C2-016,

R represents a linear or branched, saturated or unsaturated C1-020.

According to one embodiment in the formula (I):

n is 1;

the total amount of carbon atoms being more than 15 and less than 40.

According to one embodiment in the formula (I):

R1 represents a linear or branched, saturated or unsaturated C5-C15alkyl group;

R′ represents a linear or branched, saturated or unsaturated C3-C8 alkylgroup;

R represents a linear or branched, saturated or unsaturated C1-C15 alkylgroup.

According to one embodiment in the formula (I),

R1 represents a saturated linear C5-C15 alkyl group, more preferably asaturated linear C5-C12 alkyl group;

R′ represents a saturated linear C3-C8 alkyl group, more preferably asaturated linear C5-C8 alkyl group;

R represents a saturated linear or branched C5-C15 alkyl group, morepreferably a saturated linear or branched C5-C10 alkyl group.

According to one embodiment in the formula (I):

R1 represents a saturated linear C5-C10 alkyl group, more preferably asaturated linear 05-C8 alkyl group;

R′ represents a saturated linear C5-C8 alkyl group;

R represents a saturated, linear or branched C5-C10 alkyl group,preferably a saturated linear C5-C10 alkyl group.

According to one embodiment, the compound of formula (I) is a compoundof formula (Ia)

According to one embodiment, in the formula (I):

R1 represents a saturated linear or branched C5-C15 alkyl group, morepreferably a saturated linear C8-C12 alkyl group;

R′ represents a saturated linear C5-C8 alkyl group;

R represents a saturated, linear or branched 05-C10 alkyl group,preferably a saturated branched C5-C10 alkyl group.

According to one embodiment the compound of formula (I) is a compound offormula (Ib)

According to one embodiment the viscosity index improver is a polymericviscosity index improver, preferably chosen among:

polyacrylates and polymethacrylates,

olefin homopolymers or copolymers, preferably ethylene/propylene styrenecopolymers, preferably with isoprene or a diene such as butadiene,hydrogenated or not, isoprene polymers, preferably radial hydrogenatedpolyisoprene,

esterified polystyrenes, preferably esterified poly(styrene-co-maleicanhydride) mixtures of two or more of the above.

According to one embodiment the lubricant composition comprises from 0.1to 50%, preferably from 1 to 50%, more preferably from 5 to 30% byweight based on the total weight of lubricant composition, of a compoundof formula (I).

According to one embodiment the lubricant composition comprises from0.01 to 15%, preferably from 1 to 10% by weight based on the totalweight of lubricant composition, of at least one viscosity indeximprover.

According to one embodiment the lubricant composition further comprisesat least one lubricant base oil.

According to one embodiment lubricant base oil is a group III lubricantbase oil.

According to one embodiment the lubricant composition comprises from 50to 99%, preferably from 50 to 80% by weight based on the total weight oflubricant composition, of a lubricant base oil.

According to one embodiment the lubricant composition further comprisesfurther at least one lubricant additive selected from the listconsisting of detergent additives, anti-wear additives, frictionmodifiers additives, extreme pressure additives, antioxidant additives,dispersing agents, pour-point depressant additives, anti-foam agents,thickeners and mixtures of two or more thereof.

The invention also provides the use of the lubricant compositionaccording to the invention to reduce the fuel consumption of an engine,preferably of a car engine and/or to improve the cleanliness of anengine, preferably of a car engine, more preferably of at least onepiston of a car engine.

DETAILED DESCRIPTION

The present application relates to the compositions and methods forsynthesis of diester compounds for use as a base stock for lubricantapplications, or a base stock blend component for use in a finishedlubricant composition, or for the particular applications of fueleconomy and imparting cleanliness to the engines. The present diestersalso exhibit improved detergency, as determined based on the MicroCoking Test (MCT).

Fuel economy is measured as the gain in various driving cycles,especially NEDC (New European Driving Cycle), and compared totrimethylol propane ester (Nycobase 7300 (NB7300)) which is an esterknown to provide fuel economy (see e.g. Dodos, G. S., et al., Renewablefuels and lubricants from Lunaria annual. Ind. Crops Prod. (2015),http://dx.doi.org/10.1016/j.indcrop.2015.05.046 andD01:10.1080/10402004.2015.1025934).

Cleanliness is measured as a rating of piston merit, especially againstPAO which is known to be effective in cleanliness.

The diesters in accordance with the present embodiments may constitute alubricant base stock composition, or a base stock blend component foruse in a finished lubricant composition, or they may be mixed with oneor more additives for further optimization as a finished lubricant orfor a particular application. Suitable applications which may beutilized include, but are not limited to, (two-cycle) engine oils,especially car engines. The diesters in accordance with the presentembodiments may also have alternative chemical uses and applications, asunderstood by a person skilled in the art. The content of the diestersof the present embodiments may be found neat. In some aspects, finishedlubricant compositions may include between about 1 to about 25% byweight of the diester, from about 50 to about 99% by weight of alubricating base oil, and from about 1 to about 25% by weight of anadditive, especially an additive package.

Suitable non-limiting examples of additives may include detergents,antiwear agents, antioxidants, metal deactivators, extreme pressure (EP)additives, dispersants, viscosity modifiers, pour point depressants,corrosion protectors, friction coefficient modifiers, colorants,antifoam agents, demulsifiers and the like.

The diesters of the invention are preferably in combination with aviscosity improver. Viscosity improvers are known in the art and adescription thereof can be found in Chemistry and Technology ofLubricants—Editors: Mortier, Roy M., Fox, Malcolm F., Orszulik, Stefan,Ed 2010, which is incorporated herein by reference.

The viscosity improver is typically:

-   -   polyacrylates or polymethacrylates, typically referred to as        PMA,    -   olefin homopolymers or copolymers, preferably        ethylene/propylene, typically referred to as OCP (Olefin        CoPolymers)    -   styrene copolymers, preferably with isoprene or a diene such as        butadiene, hydrogenated or not, such as HSD (Hydrogenated        Styrene Diene), isoprene polymers such as SIP (Styrene Isoprene        Polymers), preferably radial hydrogenated polyisoprene (HRI),    -   esterified polystyrenes, preferably esterified        poly(styrene-co-maleic anhydride), referred to as SPE (Styrene        PolyEster),    -   mixtures of two or more of the above, especially PMA/OCP.

The amount of viscosity improver can be varied and is generally from0.01 to 15%, preferably from 1 to 10% by weight based on the totalweight of lubricant composition.

Suitable base oils can be any of the conventionally used lubricatingoils, such as a mineral oil, a synthetic oil, or a blend of mineral andsynthetic oils, or in some cases, natural oils and natural oilderivatives, all individually or in combinations thereof. Minerallubricating oil base stocks used in preparing the lubricant compositionscan be any conventionally refined base stocks derived from paraffinic,naphthenic and mixed base crudes. The lubricating base oil may includepolyolefin base stocks, of both polyalphaolefin (PAO) and polyinternalolefin (PIO) types. Oils of lubricating viscosity derived from coal orshale are also useful.

Examples of synthetic oils include hydrocarbon oils such as polymerizedand interpolymerized olefins (e.g., polybutylenes, polypropylenes,propyleneisobutylene copolymers); poly(l-hexenes), poly(l-octenes),poly(l-decenes), and mixtures thereof; alkyl-benzenes (e.g.,dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,di-(2-ethylhexyl)-benzenes); polyphenyls (e.g., biphenyls, terphenyls,alkylated polyphenyls); alkylated diphenyl ethers and alkylated diphenylsulfides and the derivatives, analogs and homologs thereof.

Alkylene oxide polymers and interpolymers and derivatives thereof wherethe terminal hydroxyl groups have been modified by esterification, andetherification, constitute another class of known synthetic lubricatingoils that can be used. These are exemplified by the oils preparedthrough polymerization of ethylene oxide or propylene oxide, the alkyland aryl ethers of these polyoxyalkylene polymers (e.g.,methyl-polyisopropylene glycol ether having a number average molecularweight of 1000, diphenyl ether of polyethylene glycol having a molecularweight of 500-1000, diethyl ether of polypropylene glycol having amolecular weight of 1000-1500) or mono- and polycarboxylic estersthereof, for example, the acetic acid esters, mixed C₃₋₈ fatty acidesters, the C₁₃ Oxo acid diester of tetraethylene glycol, or PAGs, suchas PO/BO, e.g. disclosed in WO201270007 and WO2013164457.

Another suitable class of synthetic lubricating oils that can be usedincludes the esters of dicarboxylic acids (e.g., phthalic acid, succinicacid, alkyl succinic acids, alkenyl succinic acids, maleic acid, azelaicacid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleicacid dimer, malonic acid, alkyl malonic acids, and alkenyl malonicacids) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol,dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethyleneglycol monoether, and propylene glycol). Specific examples of theseesters include dibutyl adipate, di-(2-ethylhexyl) sebacate, di-n-hexylfumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate,dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, and the complex esterformed by reacting one mole of sebacic acid with two moles oftetraethylene glycol and two moles of 2-ethylhexanoic acid. Estersuseful as synthetic oils also include those made from C5 to C12monocarboxylic acids and polyols such as neopentyl glycol, trimethylolpropane, and pentaerythritol, or polyol ethers such asdipentaerythritol, and tripentaerythritol.

Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy-, orpolyaryloxy-siloxane oils and silicate oils include another useful classof synthetic lubricants (e.g., tetraethyl silicate, tetraisopropylsilicate, tetra-(2-ethylhexyl)silicate, tetra-(4-methylhexyl)silicate,tetra-(p-tert-butylphenyl) silicate,hexyl-(4-methyl-2-pentoxy)disiloxane, poly(methyl)siloxanes, andpoly-(methyl phenyl)siloxanes). Other synthetic lubricating oils includeliquid esters of phosphorus-containing acids (e.g., tricresyl phosphate,trioctyl phosphate, and the diethyl ester of decane phosphonic acid),and polymeric tetrahydrofurans.

Unrefined, refined and re-refined oils, either natural or synthetic (aswell as mixtures of two or more of any of these) of the type disclosedhereinabove can be used as the lubricating base oil in the lubricantcomposition. Unrefined oils are those obtained directly from a naturalor synthetic source without further purification treatment. For example,a shale oil obtained directly from retorting operations, a petroleum oilobtained directly from primary distillation or ester oil obtaineddirectly from an esterification process and used without furthertreatment would be an unrefined oil. Refined oils are similar to theunrefined oils except they have been further treated in one or morepurification acts to improve one or more properties. Many suchpurification techniques are known to those skilled in the art such assolvent extraction, secondary distillation, acid or base extraction,filtration, percolation, re-refined oils are obtained by processessimilar to those used to obtain refined oils applied to refined oilswhich have been already used in service. Such re-refined oils are alsoknown as reclaimed or reprocessed oils and often are additionallyprocessed by techniques directed to removal of spent additives and oilbreakdown products.

Oils of lubricating viscosity can also be defined as specified in theAmerican Petroleum Institute (API) Base Oil InterchangeabilityGuidelines. The five base oil groups are as given in the table thatfollows. Groups I, II, and III are mineral oil base stocks. In someembodiments, the oil of lubricating viscosity is a Group I, II, III, IV,or V oil or mixtures thereof.

Saturates Sulfur VI Group I mineral oils  <90% >0.03% 80 ≤ VI < 120Groupe II ≥90% ≤0.03% 80 ≤ VI < 120 hydroprocessed oils Groupe III ≥90%≤0.03% ≥120 hydrocacked or hydroisomerized oils Groupe IVPolyalphaolefins (PAO) Groupe V All other synthetics

In one aspect, the diesters were prepared via a two-act route oftransesterification and saturated fatty acid addition. In other aspect,the diesters were prepared via a three-act route of transesterification,formic acid addition, and saturated fatty acid addition.

Transesterification is well known to those skilled in the art and can bedepicted by the following equation: RCOOR^(a)+R^(b)OH→RCOOR^(b)+R^(a)OH.The reactant esters are commonly (fatty) acid alkyl esters, includingC₁-C₂₀ (fatty) acid alkyl esters derived from a natural oil. In certainembodiments, the C₁-C₂₀ (fatty) acid alkyl esters may be unsaturatedalkyl esters, such as unsaturated fatty acid methyl esters. In furtherembodiments, such esters may include 9-DAME (9-decenoic acid methylesters), 9-UDAME (9-undecenoic acid methyl esters), and/or 9-DDAME(9-dodecenoic acid methyl esters). The transesterification reaction isconducted at approximately 60-80° C. and approximately 1 atm.

Such fatty acid alkyl esters are conveniently generated byself-metathesis and/or cross metathesis of a natural oil. Metathesis isa catalytic reaction that involves the interchange of alkylidene unitsamong compounds containing one or more double bonds (i.e., olefiniccompounds) via the formation and cleavage of the carbon-carbon doublebonds. Cross-metathesis may be represented schematically as shown inEquation I:

R^(a)—CH═CH—R^(b)+R^(c)—CH═CH—R^(d)↔R^(a)—CH═CH—R^(c)+R^(a)—CH═CH—R^(d)+R^(b)—CH═CH—R^(c)+R^(b)—CH═CH—R^(d)+R^(a)—CH═CH—R^(a)+R^(b)—CH═CH—R^(b)+R^(c)—CH═CH—R^(c)+R^(d)—CH═CH—R^(d)  (I)

wherein R^(a), R^(b), R^(c), and R^(d) are organic groups.

Self-metathesis may be represented schematically as shown in Equation IIbelow.

R^(a)—CH═CH—R^(b)+R^(a)—CH═CH—R^(b)↔R^(a)—CH═CH—R^(a)+R^(b)—CH═CH—R^(b)  (II)

wherein R^(a) and R^(b) are organic groups.

In particular, self-metathesis of natural oils or cross-metathesis ofnatural oils with olefins. Suitable olefins are internal or α-olefinshaving one or more carbon-carbon double bonds, and having between about2 to about 30 carbon atoms. Mixtures of olefins can be used. The olefinmay be a monounsaturated C₂-C₁₆α-olefin, such as a monounsaturatedC₂-C₁₀ α-olefin. The olefin may also include C₄-C₉ internal olefins.Thus, suitable olefins for use include, for example, ethylene,propylene, 1-butene, cis- and trans-2-butene, 1-pentene, isohexylene,1-hexene, 3-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and thelike, and mixtures thereof, and in some examples, α-olefins, such asethylene, propylene, 1-butene, 1-hexene, 1-octene, and the like.Non-limiting examples of procedures for making fatty acid alkyl estersby metathesis are disclosed in WO 2008/048522, the contents of which areincorporated herein by reference. In particular, Examples 8 and 9 of WO2008/048522 may be employed to produce methyl 9-decenoate and methyl9-dodecenoate. Suitable procedures also appear in U.S. Pat. Appl. Publ.No. 2011/0113679, the teachings of which are incorporated herein byreference.

The metathesis catalyst in this reaction may include any catalyst orcatalyst system that catalyzes a metathesis reaction. Any knownmetathesis catalyst may be used, alone or in combination with one ormore additional catalysts. Some metathesis catalysts may beheterogeneous or homogenous catalysts. Non-limiting exemplary metathesiscatalysts and process conditions are described in PCT/US2008/009635, PP.18-47, incorporated by reference herein. A number of the metathesiscatalysts as shown are manufactured by Materia, Inc. (Pasadena, Calif.).

Cross-metathesis is accomplished by reacting the natural oil and theolefin in the presence of a homogeneous or heterogeneous metathesiscatalyst. The olefin is omitted when the natural oil isself-metathesized, but the same catalyst types may be used. Suitablehomogeneous metathesis catalysts include combinations of a transitionmetal halide or oxo-halide (e.g., WOCI4 or WCI6) with an alkylatingcocatalyst (e.g., Me4Sn). Homogeneous catalysts may include well-definedalkylidene (or carbene) complexes of transition metals, particularly Ru,Mo, or W. These include first and second-generation Grubbs catalysts,Grubbs-Hoveyda catalysts, and the like. Suitable alkylidene catalystsmay have the following structure:

M[X¹X²L¹L²(L³)_(n)]═C_(m)═C(R^(i))R^(ii)

where M is a Group 8 transition metal, L¹, L², and L³ are neutralelectron donor ligands, n is 0 (such that L³ may not be present) or 1, mis 0, 1, or 2, X¹ and X² are anionic ligands, and R^(i) and R^(ii) areindependently selected from H, hydrocarbyl, substituted hydrocarbyl,heteroatom-containing hydrocarbyl, substituted heteroatom-containinghydrocarbyl, and functional groups. Any two or more of X¹, X², L¹, L²,L³, R^(i) and R^(ii) can form a cyclic group and any one of those groupscan be attached to a support.

First-generation Grubbs catalysts fall into this category where m=n=0and particular selections are made for n, X¹, X², L¹, L², L³, R^(i) andR^(ii) as described in U.S. Pat. Appl. Publ. No. 2010/0145086 (“the '086publication”), the teachings of which related to all metathesiscatalysts are incorporated herein by reference.

Second-generation Grubbs catalysts may also have the formula describedabove, but L¹ is a carbene ligand where the carbene carbon is flanked byN, O, S, or

P atoms, such as by two N atoms. The carbene ligand may be part of acyclic group. Examples ofsuitable second-generation Grubbs catalystsalso appear in the '086 publication.

In another class of suitable alkylidene catalysts, L¹ is a stronglycoordinating neutral electron donor as in first- and second-generationGrubbs catalysts, and L² and L³ are weakly coordinating neutral electrondonor ligands in the form of optionally substituted heterocyclic groups.Thus, L² and L³ are pyridine, pyrimidine, pyrrole, quinoline, thiophene,or the like.

In yet another class of suitable alkylidene catalysts, a pair ofsubstituents is used to form a bi- or tridentate ligand, such as abiphosphine, dialkoxide, or alkyldiketonate. Grubbs-Hoveyda catalystsare a subset of this type of catalyst in which L² and R² are linked. Aneutral oxygen or nitrogen may coordinate to the metal while also beingbonded to a carbon that is α-, β-, or γ-with respect to the carbenecarbon to provide the bidentate ligand. Examples of suitableGrubbs-Hoveyda catalysts appear in the '086 publication.

The structures below provide just a few illustrations of suitablecatalysts that may be used:

Heterogeneous catalysts suitable for use in the self- orcross-metathesis reaction include certain rhenium and molybdenumcompounds as described, e.g., by J. C. Mol in Green Chem. 4 (2002) 5 atpp. 11-12. Particular examples are catalyst systems that include Re₂O₇on alumina promoted by an alkylating cocatalyst such as a tetraalkyl tinlead, germanium, or silicon compound. Others include MoCl₃ or MoCl₅ onsilica activated by tetraalkyltins.

For additional examples of suitable catalysts for self- orcross-metathesis, see U.S. Pat. No. 4,545,941, the teachings of whichare incorporated herein by reference, and references cited therein. Seealso J. Org. Chem. 46 (1981) 1821; J. Catal. 30 (1973) 118; Appl. Catal.70 (1991) 295; Organometallics, 13 (1994) 635; Olefin Metathesis andMetathesis Polymerization by Ivin and Mol (1997), and Chem. & Eng. News80(51), Dec. 23, 2002, p. 29, which also disclose useful metathesiscatalysts. Illustrative examples of suitable catalysts include rutheniumand osmium carbene catalysts as disclosed in U.S. Pat. Nos. 5,312,940,5,342,909, 5,710,298, 5,728,785, 5,728,917, 5,750,815, 5,831,108,5,922,863, 6,306,988, 6,414,097, 6,696,597, 6,794,534, 7,102,047,7,378,528, and U.S. Pat. Appl. Publ. No. 2009/0264672 A1, andPCT/US2008/009635, pp. 18-47, all of which are incorporated herein byreference. A number of metathesis catalysts that may be advantageouslyemployed in metathesis reactions are manufactured and sold by Materia,Inc. (Pasadena, Calif.).

Natural oils suitable for use as a feedstock to generate the fatty acidalkyl esters from self-metathesis or cross-metathesis with olefins arewell known. Suitable natural oils include vegetable oils, algal oils,animal fats, tall oils, derivatives of the oils, and combinationsthereof. Thus, suitable natural oils include, for example, soybean oil,palm oil, rapeseed oil, coconut oil, palm kernel oil, sunflower oil,safflower oil, sesame oil, corn oil, olive oil, peanut oil, cottonseedoil, canola oil, castor oil, linseed oil, tung oil, jatropha oil,mustard oil, pennycress oil, camellina oil, coriander oil, almond oil,wheat germ oil, bone oil, tallow, lard, poultry fat, fish oil, and thelike. Soybean oil, palm oil, rapeseed oil, and mixtures thereof arenon-limiting examples of natural oils.

The fatty acid alkyl esters, including the unsaturated fatty acid alkylesters, are transesterified under conditions known to a person skilledin the art. Such alcohols can be represented by R—OH, where R is thedesired ester group, e.g., a shorter chain hydrocarbon, such as a C₁-C₂₀hydrocarbon, e.g. C₃-C₁₅ hydrocarbon. Such hydrocarbon may include alkylgroups, aryl groups, alkenyl groups, alkynyl groups, which may be linearor branched. In some embodiments, the alcohols may include methanol,ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec.-butanol,tert.-butanol, pentanol, isoamyl, hexanol, cyclohexanol, heptanol,2-ethyl hexanol, octanol. decanol, undecanol, dodecanol, eicosanol,

Suitable catalysts for the transesterification reaction include anyacidic, non-volatile esterification catalysts, Lewis acids, Bronstedacids, organic acids, substantially non-volatile inorganic acids andtheir partial esters and heteropolyacids. Particularly suitableesterification catalysts include alkyl, aryl or al karyl sulfonic acids,such as for example methane sulfonic acid, naphthalene sulfonic acid,p-toluene sulfonic acid, and dodecyl benzene sulfonic acid. Suitableacids may also include aluminum chloride, boron trifluoride,dichloroacetic acid, hydrochloric acid, iodic acid, phosphoric acid,nitric acid, acetic acid, stannic chloride, titanium tetraisopropoxide,dibutyltin oxide, and trichloroacetic acid. These catalysts may be usedin quantities of from about 0.1 to 5 percent by weight of the naturaloil starting material.

In some embodiments, the second act is a fatty acid addition that isperformed across the double bond(s) of the unsaturated fatty acid alkylester. In another embodiment, the third act is a fatty acid addition isperformed across the double bond(s) of the unsaturated fatty acid alkylester. The fatty acid is a saturated fatty acid, and may be a straightchain or branched acid, and in some examples, a straight chain saturatedfatty acid. Some non-limiting examples of saturated fatty acids includepropionic, butyric, valeric, caproic, enanthic, caprylic, pelargonic,capric, undecylic, lauric, tridecylic, myristic, pentadecanoic,palmitic, margaric, stearic, nonadecyclic, arachidic, heneicosylic,behenic, tricosylic, lignoceric, pentacoyslic, cerotic, heptacosylic,carboceric, montanic, nonacosylic, melissic, lacceroic, psyllic, geddic,ceroplastic acids.

The reaction of the saturated fatty acid and the unsaturated fatty acidalkyl ester is catalyzed by a strong acid. The strong acid may be aLewis Acid, a Bronsted acid, or a solid acid catalyst. Examples of suchacids include transition metal triflates and lanthanide triflates,hydrochloric acid, nitric acid, perchloric acid, tetrafluoroboric acids,or triflic acid. Acids may include alkyl, aryl or alkaryl sulfonicacids, such as methane sulfonic acid, naphthalene sulfonic acid,trifluoromethane sulfonic acid, p-toluene sulfonic acid, and dodecylbenzene sulfonic acid. Solid acid catalysts may include include cationexchange resins, such as Amberlyst® 15, Amberlyst® 35, Amberlite® 120,Dowex® Monosphere M-31, Dowex® Monosphere DR-2030, and acidic andacid-activated mesoporous materials and natural clays such a kaolinites,bentonites, attapulgites, montmorillonites, and zeolites. Thesecatalysts may be used in quantities of from about 0.1 to 5 percent byweight of the natural oil starting material.

The reaction of the saturated fatty acid and the unsaturated fatty acidalkyl ester yields a diester product and isomer mixtures thereof. Onenon-limiting reaction scheme for the aforementioned synthesis, using9-DAME as the unsaturated alkyl ester, is shown below:

In the above reaction scheme, R and R1 may be one or more of thefollowing: C₁-C₂₀ alkyl, e.g. C₃-C₂₀ alkyl, which may be linear orbranched, saturated or unsaturated. Other non-limiting diesters are tobe shown in the Examples below.

In some embodiments, the diesters were prepared via a three-act route oftransesterification, formic acid addition, and saturated fatty acidaddition.

The transesterification conditions were similar to those describedabove. The second act is the addition of formic acid across the doublebond(s) of the unsaturated fatty acid alkyl ester. Formic acid isdistinct in the category of linear monocarboxylic acids in that it isapproximately ten times more reactive that its higher carbon numberanalogues. Specifically, formic acid has a pKa value of 3.75, whereasacetic acid and propionic acid have pKa values of 4.75 and 4.87. Thesignificance of the relatively high acidity of formic acid was theaddition of formic acid to the unsaturated fatty acid alkyl ester didnot require the addition of strong acid catalysts. The omission ofstrong acid catalysts can lead to improved product quality, and theproduction of specific structural isomer products. The use of formicacid has other benefits, as in where free hydroxy species are the targetcompounds, the preparation of formyloxy esters is advantageous. Forexample, where acetic acid addition adducts are prepared, saponificationof the acetyloxy ester would generate a stoichiometric amount of acetatesalt waste. Conversely, the saponification of formyloxy esters wouldyield aqueous alkaline formate salts.

Using 9-decenoic acid methyl ester as a non-limiting example for theunsaturated fatty acid alkyl ester, formic acid was added to yield aformyloxy derivative (9-OCHO-DAME). This derivative then underwenthydrolysis to yield 9-hydroxy decanoic acid methyl ester. A reactionscheme for this process is shown below:

The hydroxyl group of the 9-hydroxy decanoic acid methyl ester is thenesterified with a saturated fatty acid and an esterification catalyst.Some non-limiting examples of saturated fatty acids include propionic,butyric, valeric, caproic, enanthic, caprylic, pelargonic, capric,undecylic, lauric, tridecylic, myristic, pentadecanoic, palmitic,margaric, stearic, nonadecyclic, arachidic, heneicosylic, behenic,tricosylic, lignoceric, pentacoyslic, cerotic, heptacosylic, carboceric,montanic, nonacosylic, melissic, lacceroic, psyllic, geddic, ceroplasticacids. The esterification catalysts may be acidic, non-volatilecatalysts, Lewis acids, Bronsted acids, organic acids, substantiallynon-volatile inorganic acids and their partial esters andheteropolyacids. Particularly suitable esterification catalysts includealkyl, aryl or alkaryl sulfonic acids, such as for example methanesulfonic acid, naphthalene sulfonic acid, p-toluene sulfonic acid, anddodecyl benzene sulfonic acid. Suitable acids may also include aluminumchloride, boron trifluoride, dichloroacetic acid, hydrochloric acid,iodic acid, phosphoric acid, nitric acid, acetic acid, stannic chloride,titanium tetraisopropoxide, dibutyltin oxide, and trichloroacetic acid.

Another non-limiting reaction scheme for the aforementioned synthesis,using 9-DAME as the unsaturated alkyl ester, is shown below:

In the above reaction scheme, R and R1 may be one or more of thefollowing: C₁-C₂₀ alkyl, e.g. C₃-C₂₀ alkyl, which may be linear orbranched, saturated or unsaturated.

Other non-limiting examples of the synthesized diesters may include thefollowing structure:

The labels indicate the origin of each component. A shorthandnomenclature can be used to describe these compositions. For the abovediester, the composition can be labeled C12/9-DA-2EH, to reference theC12 fatty acid, 9-DAME, and 2-ethyl hexanol.

Other non-limiting diesters are to be shown in the Examples below, whichmay include isomers thereof, including cis- and trans-isomers.

EXAMPLES

Acid Value: The acid value is a measure of the total acid present in anoil. Acid value may be determined by any suitable titration method knownto those of ordinary skill in the art. For example, acid values may bedetermined by the amount of KOH that is required to neutralize a givensample of oil, and thus may be expressed in terms of mg KOH/g of oil.

NOACK Volatility (TGA) is a measure of evaporative loss of a lubricatingbase oil over a period of time. The values reported were measured byASTM Method ASTM D6375-09.

Pour point was measured by ASTM Method D97-96a. Viscosity/kinematicviscosity was measured by ASTM Method D445-97. Viscosity index wasmeasured by ASTM Method D2270-93 (Reapproved 1998).

Preparation of Diester Starting Material—Procedure forTransesterification of 9-DAME Used to Prepare Various Unsaturated AlkylEsters

A 3-neck round bottom flask was fitted with a Dean-Stark trap under acondenser. The reaction vessel was charged with 1.0 molar equivalent ofthe desired unsaturated fatty acid methyl ester (FAME, e.g.methyl-9-decenoate, methyl-9-dodecenoate), 1.2 molar equivalents of thedesired alcohol (e.g. 2-ethylhexanol, 1-octanol, isobutanol), and 10 wt% octanol. The mixture was treated with 0.025 molar equivalents ofp-toluenesulfonic acid and the temperature was elevated to 130° C. Toaid removal of methanol, the headspace was continuously purged withnitrogen, and the temperature of the reaction mixture was increased 5°C. every 30 minutes until GC-FID indicated that all FAME had beenconsumed (e.g., ≤4 hour reaction time). The catalyst was quenched withan equal equivalent of KOH in water (0.1 N concentration). The mixturewas then phase separated, and the organic phase was washed with waterthree times (20 g water/100 g reaction mixture), dried with MgSO₄, andfiltered. The unsaturated esters were purified by distillation; isolatedyields may be in the range of 75-90% of the theoretical yield.

Procedure for Preparation of Diesters

In a 2-neck RBF fitted with a heating mantel and stir bar, 1.0 molequivalents of unsaturated alkyl ester with 1.25 mol equivalents of thesaturated fatty acid and 5.0 wt % triflic acid were combined. Reagentswere stirred for 18 hours at 60° C., to provide that reaction is absentof water, especially on humid days (hydrolysis of ester can cause manyside products). The triflic acid was quenched with an equal molarequivalent of 5 M KOH in water (e.g., If reaction uses 7 mmol TfOH,quench with 7 mmol of KOH in water). Water washing occurred three times,with an effort not to use any brine. A pH strip was used to provide thepH is greater than ˜6.5 before distillation (as decomposition mayoccur). Distillation occurred at <2 Torr (head temperature may be >230°C., pot temp >245° C.). Add a plug of dry basic alumina (0.5″-1″ ofalumina) to a fritted funnel and filter with a very weak vacuum (˜650Torr). If acid value was >˜0.5 mg KOH/g, repeat filtration over the sameplug of alumina. Before disposal of the alumina, stirring with 5% EtOAcin Hexanes to release residual diester occurred. This portion can bethoroughly evaporated and then combined with the bulk product. If loweracid numbers are desired, it might be useful to take up the product inhexanes prior to filtration through alumina. There are also a number ofproducts other than basic alumina which are commonly used to reduce acidnumber by filtration, e.g. Florisil—a magnesium silicate. The isolatedyield may be 35-45%.

Example 1—Caprylic (Octanoic) Acid

C8:0/2-EH-9-DA

A mixture of 2-ethylhexyl-9-decenoate (98%, 200 g, 0.708 mol) andoctanoic acid (Sigma Aldrich, ≥98%, 306 g, 2.12 mol) was treated withtrifluoromethanesulfonic acid (Sigma Aldrich, 98%, 10 g, 0.067 mol). Themixture was stirred at 60° C. for 18 h. The mixture was cooled to 25° C.and washed with 3×100 mL of saturated aqueous sodium bicarbonate and 100mL brine. The organic phase was dried over magnesium sulfate andfiltered. The product was recovered by vacuum distillation at 210°C.-220° C., 2 Torr; light fractions and bottoms were discarded. Theprecipitate was removed by vacuum filtration through a fritted funnel toprovide 103 g of colorless oil. Physical properties were reported asfollows: Kinematic Viscosity (KV) at 100° C. was 3.24 cSt, KV at 40° C.was 12.02 cSt, Viscosity Index (VI) 143, pour point <−45° C., NOACKvolatility 15 wt %.

In one particular aspect, the diester is represented by the structure

which also may be referred to herein as 2-ethylhexyl9-(octanoyloxy)decanoate.

C8:0/Octyl-9-DA

Octyl-9-decenoate (>98%, 200 g, 0.708 mol) and octanoic acid (Aldrich,≥98%, 306 g, 2.12 mol) were treated with trifluoromethanesulfonic acid(Sigma Aldrich 98%, 10 g, 0.067 mol). The mixture was stirred at 60° C.for 20 h. At room-temperature, a saturated solution of NaHCO₃ (250 mL)was added to the reaction vessel and stirred for 30 minutes. The mixturewas transferred to a separatory funnel and phase separated. The organicphase was washed with brine (200 mL×3), dried over MgSO4, and distilledat 234° C., 2 torr. The distillate was washed again with water and driedby rotary evaporation to yield 77 g of clear colorless oil. Physicalproperties were reported as follows: KV at 100° C. was 3.16 cSt, KV at40° C. was 11.3 cSt, VI 151, NOACK volatility 10 wt %. The diester maybe referred to herein as octyl-9-(octanoyloxy)decanoate. This is esterof formula I(a)

Example 2—Capric (Decanoic) Acid

C10:0/2-EH-9-DA

A mixture of 2-ethylhexyl-9-decenoate (≥98%, 400 g, 1.42 mol) anddecanoic acid (Aldrich, ≥98%, 489 g, 2.83 mol) was treated withtrifluoromethanesulfonic acid (20 g, 0.133 mol). The mixture was stirredat 60° C. for 20 h. The mixture was cooled to 25° C. and quenched with150 mL of 1M KOH which resulted in formation of a precipitate. Water wasadded to the mixture and stirred rigorously. The resulting emulsion wastransferred to a separation vessel and phase separated. The mixture waswashed continuously with 5×150 mL H2O. The product was recovered byvacuum distillation at 225° C., 2 Torr; light fractions and bottoms werediscarded. Distillation yielded 223.1 g of product as a mixture ofisomers, 99% pure by GC-FID. Physical properties were reported asfollows: KV at 100° C. was 3.6 cSt, KV at 40° C. was 14.1 cSt, VI 145,pour point <−45° C., NOACK volatility 10 wt %. C10:0/2-EH-9-DA

A mixture of 2-ethylhexyl-9-decenoate (≥98%, 800 g, 2.83 mol) anddecanoic acid (Aldrich, ≥98%, 490.2 g, 2.84 mol) was treated withtrifluoromethanesulfonic acid (Aldrich, ≥98%, 40 g). The mixture wasstirred at 60° C. for 20 h. The reaction mixture was then cooled to roomtemperature and 67 g of NaHCO₃ was added. The suspension was stirredcontinuously for >24 hours, until pH strip indicated pH ≥6(neutralization is also indicated by bleaching of the dark reactionmixture to yellow). The mixture was gravity filtered, and the productwas recovered by vacuum distillation at 224° C., 2 Torr; startingmaterials were recovered as light fractions and the bottoms werediscarded. The major fraction was gravity filtered to yield the productas a colorless oil (397 g, 0.87 mol). Light fractions duringdistillation were combined to provide a 512 g mixture containing2-ethylhexyl-9-decenoate (69 w % by GC-FID) and decanoic acid (26 w % byGC-FID). The entire quantity was treated with trifluoromethanesulfonicacid (Aldrich, 98%, 10 g) and stirred for 18 h at 60° C. At roomtemperature, the mixture was stirred with NaHCO₃ (17 g, 0.2 mol) untilpH ≥6. Purified by vacuum distillation at 224° C., 2 Torr to give theproduct as a colorless oil (170 g, 0.37 mol). The product fractionsobtained over two reactions were combined and purity was verified byGC-FID. Physical properties were reported as follows: KV at 100° C. was3.6 cSt, KV at 40° C. was 14.0 cSt, VI 146, pour point <−45° C., NOACKvolatility 10%.

Example 3—Lauric Acid

C12:0/2-Ethylhexyl-9-Decenoate

A mixture of 2-ethylhexyl-9-decenoate (≥98%, 200 g, 0.708 mol) anddodecanoic acid (Sigma Aldrich, ≥98%, 425 g, 2.12 mol) was heated to 60°C. then treated with trifluoromethanesulfonic acid (Sigma Aldrich, ≥98%,10 g, 0.067 mol). The reaction was stirred at 60° C. for 22 h. Thereaction mixture was then cooled to 45° C. and 100 mL of hexanes wasadded. The contents of the reaction vessel was transferred to a dropfunnel and dodecanoic acid was recrystallized out of solution bydropwise addition of the mixture into isopropanol at −20° C. Theresulting suspension was vacuum filtered through Whatman 6 filter paper.The filtrate was concentrated in vacuo and the oil was washed with a 0.1M aqueous solution of K₂CO₃ until pH was 7, then washed with water. Theorganic phase was dried over Na₂SO₄ then purified by vacuum distillationat 218° C., 0.1 Torr to give 69 g of oil. The distillate was passedthrough a bed of Al₂O₃ to give a clear colorless oil. KV at 100° C. was3.97 cSt, KV at 40° C. was 15.62 cSt, VI 160.6, pour point −40° C.,NOACK volatility 5.5 wt %. The synthesized diester may be referred to as10-[(2-ethylhexyl)oxy]-10-oxodecan-2-yl dodecanoate. This is ester offormula I(b).

C12:0/iBu-9-Decenoate

Isobutyl-9-decenoate (≥98%, 399.2 g) and dodecanoic acid (Sigma Aldrich,≥98%, 1056 g, 5.3 mol) were combined. The mixture was heated to 60° C.then treated with trifluoromethanesulfonic acid (Sigma Aldrich, 20 g,0.13 mol). The reaction was stirred at 60° C. for 22 h. Lauric acid wasprecipitated by dropwise addition of the reaction mixture into a dry icebath of isopropanol. The suspension was cold-filtered. The filtrate wasconcentrated in vacuo then transferred into a separatory funnel andwashed with water (150 mL×7). The organic phase was dried with Na₂SO₄,and purified by distillation. The major fraction was obtained as 292 gof oil at 215° C., 0.1 Torr. The distillate was filtered through basicalumina. KV at 100° C. was 3.35 cSt, KV at 40° C. was 12.24 cSt, VI 154,pour point <−18° C., NOACK volatility 12 wt %.

C10:0/2-Ethylhexyl-9-Dodecenoate

2-ethylhexyl-9-dodecenoate (≥98%, 416 g, 1.47 mol) and dodecanoic acid(Sigma Aldrich, ≥98%, 357 g, 2.07 mol) were treated withtrifluoromethanesulfonic acid (Sigma Aldrich, 98%, 20 g, 0.13 mol) andstirred at 60° C. for 18 h. The reaction was cooled to 25° C. whilestirring and the catalyst was quenched within the reaction vessel bydropwise addition of KOH solution (7.5 g KOH in 75 mL H2O). The mixturewas transferred to a separatory funnel and phase separated. The organicphase was washed with of DI water (200 mL×2), dried over MgSO₄, andfiltered. The product was purified by distillation at 224° C., <1 Torrand vacuum filtration through Al₂O₃ on a fritted funnel at 650 Torr toyield 230 g of clear yellowish oil. KV at 100° C. 3.9 cSt, KV at 40° C.15.7 cSt, VI 149, pour point <−45° C., NOACK volatility 6.0 wt %.

C12:0/2-Ethylhexyl-9-Decenoate

9-OH-2-Ethylhexyldecanoate (50 g, 0.17 mol), dodecanoic acid (40 g),methanesulfonic acid (0.8 g) and toluene (200 mL) were added to a 500 mL3-necked round-bottom flask at 23° C. under an atmosphere of air. Theflask was then fitted with a thermocouple temperature regulator withheating mantle, Dean-Stark distillation trap with water condenser. Thetop of the condenser was fitted with a rubber stopper with nitrogenneedle inlet. Through the headspace of the apparatus was passed N₂ (flowrate=2.5 ft³/hr) for 10 minutes, and subsequently, the temperature wasincreased to 125° C. After approximately 8 hours approximately 3 mL ofwater was collected in the trap and the Dean-Stark trap was replacedwith a distillation head and receiving flask and the toluene was removedvia distillation. Vacuum (2 Torr) and the temperature was increased to150° C. to remove the excess dodecanoic acid. After 1 hour no moredistillate was observed and the crude product was filtered through basicalumina oxide. The product was isolated as a slight yellow oil, 45 g(55%). KV at 100° C. 3.9 cSt, KV at 40° C. 15.78 cSt, VI 157, pour point<−45° C.

Each of the three components of the diester compositions (methyl ester,alcohol, and saturated fatty acid) impart predictable performancequalities on the final structure. Thus, the properties of a diester maybe tuned to fit within specific performance specifications by carefullyselecting the combination of starting materials.

Example 4—Formic Acid Methyl-9-Decenoate/Formic Acid

Methyl-9-decenoate (50 g, 0.27 mol) and formic acid (100 mL) were addedto a 250 mL 2-necked round bottom flask at 23° C. under an atmosphere ofair. The flask was then fitted with a thermocouple temperature regulatorwith heating mantle and water condenser. The top of the condenser wasfitted with a rubber stopper with nitrogen needle inlet. Through theheadspace of the apparatus N₂ (flow rate=2.5 ft³/hr) for 10 minutes, andsubsequently, the temperature was increased to 105° C. Afterapproximately 15 hours, the heating source was removed and the reactionwas allowed to cool to ambient temperature. An aliquot was taken forGCMS (method GCMS1) to evaluate conversion. The reaction mixture wastransferred to a single-neck round bottom flask and the excess formicacid was removed by rotorary evaporator (50 Torr, 35° C.). 9-OCHO-DAMewas obtained as a slight yellow/brown oil, 60.15 g (97%) and usedwithout further purification.

2-Ethylhexyl 9-Decenoate/Formic Acid

2-Ethylhexyl 9-decenoate (282 g, 1 mol) and formic acid (460 g) wereadded to a 2 L 3-necked round-bottom flask at 23° C. under an atmosphereof air. The flask was then fitted with a thermocouple temperatureregulator with heating mantle and water condenser. The top of thecondenser was fitted with a rubber stopper with nitrogen needle inlet.Through the headspace of the apparatus was passed N₂ (flow rate=2.5ft³/hr) for 10 minutes, and subsequently, the temperature was increasedto 105° C. After approximately 15 hours, additional formic acid (200 g)was added and the reaction was continued. Following an additional 24hours the heating source was removed and the reaction was allowed tocool to ambient temperature. An aliquot was taken for GCMS (methodGCMS1) to evaluate conversion. The reaction mixture was transferred to asingle-neck round bottom flask and the excess formic acid was removed byrotorary evaporator (50 Torr, 35° C.), followed by vacuum distillation(2 Tarr, 125° C.). 9-OCHO-2-ethylhexyldecanoate was obtained as a slightyellow/brown oil, 320 g (97%). In a single neck, 1 Liter round-bottomflask was added 9-OCHO-DAEH and 6 M aqueous potassium hydroxidesolution. The reaction flask was fitted with a reflux condenser andheated to reflux for 24 hours. The reaction was allowed to cool, thelayers were separated and the organic product was dried by vacuumstripping (5 Torr, 100° C.) for 1 hour to obtain the desired9-OH-2-ethylhexyldecanoate as a slight brown oil, 275 g (91%).

The table below shows the physicochemical characteristics of esters offormulas I(a) and I(b). These esters were compared with various baseoils. These esters are thus compared to a group III base oil (YUBASE4)and to a trimethylol propane ester known for good performance (NYCOBASE7300 or NB7300).

TABLE 1 Physicochemical characteristics of esters of formulas I(a) andI(b) in comparison with other base oils. Characteristic Method UnitsYUBASE4 NB7300 ESTER I(a) ESTER I(b) KV 40° C ASTM mm²/s 19.4 14 11.315.62 D445-97 KV 100° C. ASTM mm²/s 4.24 3.4 3.16 3.97 D445-97 VI ASTMNo unit 126 118 151 160 D2270-93 VI: Viscosity index KV: Kinematicviscosity

The two esters were evaluated in 0W-20 engine formula, together with aknown additive package, namely Pack Infineum P6660. SV261 is a known VIimprover of Infineum, which is a Poly Isobutene Styrene Hydrogenated(PISH). Infineum V385 is a known Pour Point Depressant.

The formulas prepared are grade 0W-20 formulas. They were carried out atiso-HTHS (2.6 mPa·s). HTHS is the value at High Temperature High Shear.The compositions and characteristics of the formulas tested are given inthe table below

Composition Comp Ester I(a) Ester I(b) P6660 13.30 13.30 13.30 SV2613.60 3.60 3.60 INFINEUM 0.20 0.20 0.20 V385 YUBASE 4 82.90 72.90 72.90ESTER I(a) 10.00 ESTER I(b) 10.00

Physicochemical characteristics Ex Comp Ester I(a) Ester I(b) KV at 40°C. mm²/s 44.26 40.70 42.63 KV at 100° C. mm²/s 8.311 7.828 8.179 VI NoUnit 166 166 170 HTHS mPa · s 2.59 2.6 2.60 Density (15° C.) kg/m³ 849.7861.1 856.6 CCS (−35° C.) mPa · s 6520 5340 5750 ASTM D5293 MRV mPa · s54600 30600 34300 (ASTM D4684)

The compositions according to the invention (Ester I(a) and Ester I(b))have an improved «cold» behaviour.

Detergency

A Micro Coking Test (MCT) is performed to assess the detergency of theesters of the invention. The standard applied is GFC-Lu-027-T-07.

The results are in the below table.

MCT test Ex Comp Ester I(a) Ester I(b) Cotation meth 7.1 7.8 8.4 Temp atinitial point 252 254 249

Engine Tests.

Engine cleanliness.

The following compositions are prepared.

Composition Comp. Ester I(a) Ester I(b) Additive package 10.9 10.9 10.9SV261 6.5 6.5 6.5 MoDTC 0.1 0.1 0.1 YUBASE 4+ 62.5 62.5 62.5 YUBASE 610.0 10.0 10.0 PAO 4 10.0 ESTER I(a) 10.0 ESTER I(b) 10.0

Physicochemical characteristics Ex Comp I(a) I(b) KV at 40° C. mm²/s53.16 50.34 50.87 KV at 100° C. mm²/s 9.93 9.74 9.76 VI No Unit 176 183181 HTHS mPa · s 2.9 2.88 2.9

The test that is used to determine cleanliness is based on the pistonmerit. Each lubricant composition (10 kg) was evaluated in a test ofcleanliness diesel common rail (common rail) for automobile. The engineis a 1.4 L 4 cylinders engine. Its power is 80 kW. The cycle time of thetest is 96 hours, alternating idle and 4000 rpm regime. The temperatureof the lubricating composition is 145° C. and the temperature of thecooling water system is 100° C. No drain nor any extra to lubricatingcomposition is made during the test. Fuel EN590 is used. The test isperformed in two phases for a total of 106 hours and in a first rinsingstep and lapping for 10 hours and then in a second step with thecomposition to be evaluated (4 kg), and finally according to anendurance step with a duration of 96 hours with the composition to beevaluated (4 kg). During the test, one evaluates the physicochemicalparameters of the lubricant. Then the lubricant consumption duringlapping and during the test.

The results are summarized in the below table.

Ex. Co-base Piston Comp. PAO 65.75 Ester I(a) Ester I(a) 70.76 EsterI(b) Ester I(b) 72.27

The choice of the reference (PAO) is correct with a score of 65 which isalready high as is expected for PAOs. The present esters are thuscompared to a good formula for a cleanliness standpoint, and it can beseen that the esters I(a) and I(b) improve both this scoring value by 5and 7 points, respectively.

Fuel Economy

The following compositions are prepared. OLOA 249SX is an over-basedsulphonate detergent from Oronite.

Composition Comp. Ester I(a) Ester I(b) Additive package 10.6 10.6 10.6SV261 6.2 6.2 6.2 MoDTC 0.5 0.5 0.5 OLOA 249SX 0.7 0.7 0.7 YUBASE 4+72.0 72.97 72.7 NICOBASE 7300 10.0 ESTER I(a) 9.03 ESTER I(b) 9.3

Physicochemical characteristics Ex Comp I(a) I(b) KV at 40° C. mm²/s41.25 42.04 43.28 KV at 100° C. mm²/s 8.43 8.51 8.64 VI No Unit 187 185183 HTHS mPa · s 2.62 2.59 2.63

The test is run on an engine of 2.0 L displacement and maximum power 180kW, driven by an electric motor generator. The various lubricantcompositions are compared with a reference lubricating composition (SAE0W-30). Each friction measurement is performed for about 12 hours andenables a detailed mapping of the friction torque induced by eachlubricant composition. The tests are performed in the followingsequence:

-   -   rinsing of the engine with a rinsing oil with detergents as        additive followed by rinsing with the lubricant reference        composition,    -   friction measurement of torque at four temperatures with the        reference composition,    -   rinsing of the engine with a rinsing oil with detergents as        additive followed by rinsing with the lubricating composition to        be evaluated,    -   friction measurement of torque at four temperatures with the        lubricating composition to be evaluated,    -   rinsing of the engine with a rinsing oil with detergents as        additive followed by rinsing with the reference composition,    -   friction measurement of torque at four temperatures with the        lubricant reference composition,

The ranges of variation of the regime and the temperature levels werechosen to cover the most representative operating points of the NEDCcertification cycle. 4 selected temperature levels are consistent withthe cycles considered.

The instructions implemented are:

-   -   water temperature in engine output: 40° C./60° C./90° C./110°        C.±2° C.,    -   oil temperature ramp: 40° C./60° C./90° C./110° C.±2° C.,    -   air temperature at the inlet: 21° C.±2° C.    -   backpressure at exhaust: 40 mbar at 4000 rpm

Friction gain is evaluated for each lubricant composition according tothe temperature and the engine speed measured and compared to frictionfor the lubricant reference composition.

From these friction gains and after processing by a transfer function,it is estimated friction gains and loss on the NEDC standardizedapproval cycle resulting from the use of lubricating compositions

Ex. Gain/Loss Ester I(a) −0.03% Ester I(b) −0.05%

The choice of the reference (NB7300) is driven by the fact that NB7300is known for providing elevated fuel economy. The results indicate thatthe three formulas are at least equivalent, if not better, from a fueleconomy standpoint with gains of 0.05% and 0.03%.

1. Lubricant composition comprising at least one compound of formula (I)below and at least one viscosity index improver

wherein: n is below 1.1 R1 represents a linear or branched, saturated orunsaturated C3-C20, R′ represents a linear or branched, saturated orunsaturated C2-C16, R represents a linear or branched, saturated orunsaturated C1-C20.
 2. Lubricant composition of claim 1, wherein in theformula (I): n is 1; the total amount of carbon atoms being more than 15and less than
 40. 3. Lubricant composition of claim 1, wherein in theformula (I): R1 represents a linear or branched, saturated orunsaturated C5-C15 a Iky I group; R′ represents a linear or branched,saturated or unsaturated C3-C8 a Iky I group; R represents a linear orbranched, saturated or unsaturated C1-C15 alkyl group.
 4. Lubricantcomposition according to claim 1, wherein in the compound of formula(I), R1 represents a saturated linear C5-C15 alkyl group, morepreferably a saturated linear C5-C12 alkyl group; R′ represents asaturated linear C3-C8 alkyl group, more preferably a saturated linearC5-C8 alkyl group; R represents a saturated linear or branched C5-C15alkyl group, more preferably a saturated linear or branched C5-C10 alkylgroup.
 5. Lubricant composition according to claim 1, wherein in theformula (I): R1 represents a saturated linear C5-C10 alkyl group, morepreferably a saturated linear C5-C8 alkyl group; R′ represents asaturated linear C5-C8 alkyl group; R represents a saturated, linear orbranched C5-C10 alkyl group, preferably a saturated linear C5-C10 alkylgroup.
 6. Lubricant composition according to claim 5, wherein thecompound of formula (I) is a compound of formula (Ia)


7. Lubricant composition according to claim 1, wherein in the formula(I): R1 represents a saturated linear or branched C5-C 5 alkyl group,more preferably a saturated linear C8-C12 alkyl group; R′ represents asaturated linear C5-C8 alkyl group; R represents a saturated, linear orbranched C5-C10 alkyi group, preferably a saturated branched C5-C10alkyl group.
 8. Lubricant composition according to claim 7, wherein thecompound of formula (I) is a compound of formula (Ib)


9. Lubricant composition according to claim 1, wherein the viscosityindex improver is a polymeric viscosity index improver, preferablychosen among: polyacrylates and polymethacrylates, olefin homopolymersor copolymers, preferably ethylene/propylene styrene copolymers,preferably with isoprene or a diene such as butadiene, hydrogen ated ornot, isoprene polymers, preferably radial hydrogenated polyisoprene,esterified polystyrenes, preferably esterified poiy(styrene-co-maleicanhydride) mixtures of two or more of the above.
 10. Lubricantcomposition according to claim L comprising from 0, 1 to 50%, preferablyfrom 1 to 50%, more preferably from 5 to 30% by weight based on thetotal weight of lubricant composition, of a compound of formula (I). 11.Lubricant composition according to claim 1, comprising from 0.01 to 15%,preferably from 1 to 10% by weight based on the total weight oflubricant composition, of at least one viscosity index improver. 12.Lubricant composition according to claim 1, further comprising at leastone lubricant base oil.
 13. Lubricant composition according to claim 1,wherein the lubricant base oil is a group III lubricant base oil. 14.Lubricant composition according to claim 1, comprising from 50 to 99%,preferably from 50 to 80% by weight based on the total weight oflubricant composition, of a lubricant base oil.
 15. Lubricantcomposition according to claim 1, further comprising at least onelubricant additive selected from the list consisting of detergentadditives, anti-wear additives, friction modifiers additives, extremepressure additives, antioxidant additives, dispersing agents, pour-pointdepressant additives, anti-foam agents, thickeners and mixtures of twoor more thereof.
 16. Use of a lubricant composition according to claim1, to reduce the fuel consumption of an engine, preferably of a carengine and/or to improve the cleanliness of an engine, preferably of acar engine, more preferably of at least one piston of a car engine.